Description
We point out the existence of a new type of topological
Josephson effect involving type II superconductors and three-
dimensional topological insulators as tunnel junctions. We
predict that vortex lines induce a variant of the Witten effect
that is the consequence of the axion electromagnetic
response of the topological insulator: at the interface of the
junction each flux quantum attains a fractional electrical
charge of e/4. As a consequence, if an external magnetic field
is applied perpendicular to the junction, the Witten effect
induces an ac Josephson effect in the absence of any external
voltage. We derive a number of further experimental
consequences and propose potential setups where these
quantized, flux induced Witten effects may be observed [1].
[1] Physical Review Letters 117, 167002 (2016)
